The determination of the positioning of a point in space and the determination of the attitude of an arbitrary object are problems relating to numerous technical fields.
The various solutions generally afforded must resolve any ambiguity in position or attitude, cater for more or less severe dynamics of the systems and satisfy high accuracy, in particular in the aeronautical field.
In systems for detecting position and attitude of objects in space catering for an accuracy of a few millimeters in position and degree in attitude, numerous applications exist in various fields.
These systems are used in aeronautics, for detecting head posture, notably for the helmets of fighter aircraft, of military, civilian or para-civilian helicopters. They are also used for the detection of simulation helmets, this detection can then be combined with an oculometry device, also called an eyetracker, for detecting the position of the gaze. Numerous applications of these systems also exist in the field of virtual reality and games.
A known solution is the use of a video projector projecting in space test grids comprising patterns in a zone comprising an object the kinematics of which are sought. In the latter case the object comprises sensors which can be disposed for example in parallelogram fashion.
Patent WO 2008/028877 describes a method for detecting the orientation and the position of an object in space. This patent describes two variant embodiments.
A first variant embodiment describes a video image projector with laser source illuminating two lineal sensors positioned on a helmet and disposed in parallel in such a way that their ends form a parallelogram. The video image projector projects test grids comprising particular patterns in a zone comprising the sensors.
This first variant makes it possible to perform a first calculation which, on the basis of the points of impact of the laser beams on the lineal sensors, provides the position, in an image plane of the projector, of the mappings of the ends of the sensors. A second calculation makes it possible to provide, on the basis of these projections, the orientation and the position of the parallelogram formed by ends of the sensors.
The second variant embodiment describes a camera filming four light-emitting diodes mounted in parallelogram fashion on an object. A calculation which on the basis of the projected images of these diodes on the image plane of the camera sensor makes it possible to provide the orientation and the position of the parallelogram positioned on the helmet.
Nevertheless these solutions present drawbacks. Notably, the aforementioned first variant embodiment requires bulky devices on the object. Moreover, it may require an objective for angularly expanding the image produced by the imager, of LCOS type for example. Another drawback is that each sensor requires its associated sequential reading device. Finally, the optical signal to be provided is modulated spatially in the form of test grids.
The aforementioned second solution requires at least one camera, namely:                a bidimensional photosensor of mosaic type and its associated sequential reading device;        an objective for forming the images of the four diodes on the plane of the photosensor.        
Moreover, the light-emitting diodes positioned on the object emit optical radiation, the source of electrical power consumption. This radiation is, on the one hand, not used by the camera and on the other hand, part of the luminous energy is emitted out of the flight deck rendering the aeroplane configuration detrimental to stealth.